1. Field of the Invention
The present invention relates to a character image generator and, especially to a character image generator capable of transforming certain type of external character images to another type of images rotated by 90 degrees.
2. Description of the Prior Art
In a character image generator, there is provided at least one font memory wherein individual bit images of characters to be generated are stored. These bit images are designed according to a predetermined font. Each bit image is formed in a memory area defined, for example, by 24 bits (horizontal or width).times.40 lines (vertical or height).
In a character image generator, character code data transmitted from a host data processor such as a host computer are stored in a text-buffer once. Then, character code data stored in the text buffer are read out therefrom serially and bit images corresponding to character codes are outputted to a printer which are obtained by reading out bit images stored in a font memory.
There are provided many available fonts and every user can choose a desirable one among them. Every font has two types with respect to the orientation of each character. In one type, every bit image is oriented in a vertical direction (portrait type) and, in another type, every bit image is oriented in a horizontal direction (landscape type) which is obtained by rotating every bit image of portrait type in a clock-wise direction by 90 degrees. In other words, the former bit image of portrait type is formed, for example, in a memory area defined by 24 dots (horizontal).times.40 lines (vertical) and the latter one is formed in a memory area, for example, defined by 40 dots (horizontal).times.24 lines (vertical).
The font memory has a RAM for loading down bit images of external or special characters from the host data processor which are not registered in a ROM of the font memory for memorizing bit images of characters naturally contained in the font. In said ROM of the font memory, bit images of two types (portrait type and landscape type) are stored as one set. However, as far as individual external characters are concerned, bit images of two types with respect to each external character are not usually provided upon registering an external character. Therefore, it becomes necessary to transform every bit image of a first type to a bit image of a second type by the host data processor in order to transmit bit images of both types to the font RAM. Accordingly, for instance, in such a case that characters are to be printed on a cut paper in a landscape format namely along column lines, bit images of landscape type become necessary which are obtained by rotating respective bit images of portrait type by 90 degrees. Therefore, if a user wishes to register an external character desired in the font RAM, it is required for him to prepare not only a bit image of portrait type but also a bit image of landscape type in order to send both bit images to the printer.